Reflectance confocal microscopy: Presurgical margin assessment improves lentigo maligna and lentigo maligna melanoma management

Abstract

Elshot et al.¹ emphasized in their article a cardinal subject in the management of Lentigo maligna (LM) and Lentigo maligna melanoma (LMM), a subtype of melanoma which commonly occurs on sun-exposed skin of the face, scalp and neck region, especially in elderly men. It is known to be associated with a noticeable incomplete excision rate and a significant recurrence rate after wide local excision (WLE).² The main explanation for these issues is LM/LMM subclinical extension, invisible to clinical examination using dermoscopy and Wood's lamp, leading to an underestimation of its actual size. This study's main objective is to investigate the influence of presurgical mapping of biopsy-proven LM/LMM with handheld reflectance confocal microscopy (HH-RCM) with a focus on surgical treatment, follow-up outcomes and management decisions.

The promising results of this research draw attention on how HH-RCM could become a standard of care in the surgical and also non-surgical management of LM and LMM. One of the most striking, and promising, findings is that the resection margins after WLE in the presurgical HH-RCM group were cleared in 96.5% of cases. Moreover, this exceptional clearance rate was also associated with a median histologic margin of 3.0 mm which, if achieved, is expected to significantly reduce risk of local recurrence.²

It has to be acknowledged that the local recurrence rate of 1.4% in this study is potentially due to a shorter follow-up as observed in previous studies stating longer post-interventional observation periods with local recurrence rates ranging from 8% to 20%.²

According to another finding, RCM detected in 60% of the cases subclinical atypical cells beyond the initial surgical margins which underlines the superiority of RCM compared to clinical examination with dermoscopy alone.³ Identifying subclinical extent goes hand in hand with an increased lesion size. It is arguable that this clinical underestimation of the actual lesion size is introducing lower histologic clearance rates after wide local excision (WLE) and higher recurrence rates due to a smaller extent of the histologic margins.

Additionally, the authors reported that 75% of initially misdiagnosed LM were actually invasive melanomas highlighting another interesting aspect of RCM mapping: Despite the limited visualization of deeper skin structures down to a depth of around 200 μm, RCM has still the potential to identify invasive LMM components.⁴

Identifying invasive or subclinical components and a refusal of (further) surgery are the most common reasons for a modified management such as an adaption of the surgical method, treatment with topical imiquimod or radiation therapy. In all these scenarios, presurgical HH-RCM margin assessment with a described median mapping duration in this study of only 14 minutes (range 4–50) may lead to a more tailored treatment approach adjusting to the individual needs of a patient. Taking into account that in cosmetic sensitive areas, such as the face, the achievement of adequate wide excision margins with the reconstruction of the subsequent defect could be technically challenging inflicting additional morbidity, and may result in an unacceptable cosmetic outcome. All of this needs to be taken into consideration, especially on a background of a rising incidence of LM/LMM cases affecting a younger population which has been observed in many Western countries, including Australia where LM has become the most common form of melanoma in situ.⁵ The rate of transformation of LM to LMM is low and tailoring management on patient-centric outcomes with non-invasive options is in our opinion the way of the future.

The authors declare no conflict of interest.